import pyautogui
from PIL import Image

def screenshot_region_to_file(region, filename):
    """
    Takes a screenshot of a given screen region and saves it to a file.

    :param region: A tuple of four integers representing the screen region (left, top, width, height).
    :param filename: The name of the file to save the screenshot to.

    :return: An Image object representing the screenshot.
    """
    screenshot = pyautogui.screenshot(region=region)
    screenshot.save(filename)
    return screenshot
